Change of plasma basic phenomena accompanied by electron temperature decrease

提出了一种在不改变气压和放电功率的情况下控制低压放电等离子体电子温度的新方法，并对其物理机制进行了研究。电子温度连续控制在5 eV到0.04 eV之间。结果表明：1)通过改变空心阴极的结构或在放电等离子体中偏置栅极来实现能量控制。2)冷电子是由于高能电子通过负偏置栅格而产生的电离。3)从电子能量分布来看，-5 eV电子的累积电离是产生冷电子的重要机制。4)径向分布在直径30厘米以上的5%范围内具有良好的均匀性。5)能量控制也可能发生在直流放电、微波放电和射频放电中。6)气体物种(Ar、He、7)在甲烷反应等离子体中，随着电子温度的降低，负氢离子和甲基自由基的生成增加。这一现象不仅适用于过程等离子体的能量控制，也适用于基本的等离子体实验。

A novel method for a control of electron temperature of low pressure discharge plasmas, without changing pressure and discharge power, is developed and the physical mechanism is investigated. The electron temperature is controlled continuously from 5 eV to 0.04 eV. The results are summarized as follows:1) The energy control is performed by changing a construction of hollow cathode or biasing a grid in a discharge plasma.2) Cold electrons are generated by an ionization due to high energy electrons passing through a negatively biased grid.3) From the electron energy distribution, cumulative ionization due to the electrons of -5eV is an important mechanism for producing cold electrons.4) Radial profile has a good uniformity within 5 % over 30 cm in diameter.5) The energy control is possible to occur in a DC discharge, a microwave discharge, and an RF discharge as well.6) The gas species (argon, helium, hydrogen) are not intrinsical factor for the energy control.7) In reactive plasmas with methane we observe enhanced productions of negative hydrogen ion and methyl radical with a decrease in the electron temperature.The phenomena investigated here are applicable to the energy control of the processing plasma as well as the basic plasma experiments.